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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-new-crypto-transforms"></a>Cryptographic transforms.</h2></div></div></div>
<p>The cryptographic transforms (digests, signatures and encryption)
	implementation is the main goal of "xmlsec-&lt;crypto&gt;" library.
	Most of the cryptographic <a class="link" href="xmlsec-notes-transforms.html" title="Transforms and transforms chain.">transforms</a> 
	use default <em class="structfield"><code>pushBin</code></em> and <em class="structfield"><code>popBin</code></em> 
	methods and provide custom <a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a> method. 
	The binary transform <a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a> method 
	processes data from the input buffer
	<em class="structfield"><code>inBuf</code></em> and pushes results to
	<em class="structfield"><code>outBuf</code></em>. The transform should try to
	consume and remove data from <em class="structfield"><code>inBuf</code></em> buffer
	as soon as the data became available. However, it might happen
	that current data size in the input buffer is not enough (for example,
	RSA-PKCS1 algorithm requires that all the data are available in 
	one buffer). In this case, transform might keep the data in the 
	input buffer till the next call to 
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a>
	method. The "last" parameter of the 
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a>
	indicates that transform MUST process all the data in the input buffer
	and return as much as possible in the output buffer. The 
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a> method 
	might be called multiple times with non-zero "last" parameter until 
	the transforms returns nothing
	in the output buffer. In addition, the transform implementation is 
	responsible for managing the transform <em class="structfield"><code>status</code></em> 
	variable.
	</p>
<div class="table">
<a name="id-1.2.14.6.2.13"></a><p class="title"><b>Table 2. Typical transform status managing.</b></p>
<div class="table-contents"><table class="table" summary="Typical transform status managing." border="1">
<colgroup>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td>xmlSecTransformStatusNone</td>
<td>Transform initializes itself (for example, cipher transform 
	generates or reads IV) and sets <em class="structfield"><code>status</code></em> 
	variable to xmlSecTransformStatusWorking.</td>
</tr>
<tr>
<td>xmlSecTransformStatusWorking</td>
<td>Transform process the next (if "last" parameter is zero) or
	last block of data (if "last" parameter is non-zero).
	When transform returns all the data, it sets the 
	<em class="structfield"><code>status</code></em> variable to 
	xmlSecTransformStatusFinished.</td>
</tr>
<tr>
<td>xmlSecTransformStatusFinished</td>
<td>Transform returns no data to indicate that it finished
	processing.</td>
</tr>
</tbody>
</table></div>
</div>
<p><br class="table-break">	
	</p>
<p>In adition to <a class="link" href="xmlsec-transforms.html#xmlSecTransformExecuteMethod" title="xmlSecTransformExecuteMethod ()">execute</a>
	methods, signature, hmac or digest transforms 
	MUST implement <a class="link" href="xmlsec-transforms.html#xmlSecTransformVerifyMethod" title="xmlSecTransformVerifyMethod ()">verify</a> method. 
	The <a class="link" href="xmlsec-transforms.html#xmlSecTransformVerifyMethod" title="xmlSecTransformVerifyMethod ()">verify</a> method is called
	after transform execution is finished. The 
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformVerifyMethod" title="xmlSecTransformVerifyMethod ()">verify</a> method implementation 
	must set the "status" member to <a class="link" href="xmlsec-transforms.html#xmlSecTransformStatusOk">xmlSecTransformStatusOk</a>
	if signature, hmac or digest is successfuly verified or to
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformStatusFail">xmlSecTransformStatusFail</a>
	otherwise.
	</p>
<p>The transforms that require a key (signature or encryption 
	transforms, for example) MUST imlpement 
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformSetKeyRequirementsMethod" title="xmlSecTransformSetKeyRequirementsMethod ()">setKeyReq</a> 
	(prepares the <a class="link" href="xmlsec-keys.html#xmlSecKeyReq" title="struct xmlSecKeyReq">key requirements</a>
	for key search) and
	<a class="link" href="xmlsec-transforms.html#xmlSecTransformSetKeyMethod" title="xmlSecTransformSetKeyMethod ()">setKey</a> 
	(sets the key in the transform) methods. 
	</p>
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